An Automated Machine Learning Approach to the Retrieval of Daily Soil Moisture in South Korea Using Satellite Images, Meteorological Data, and Digital Elevation Model

Authors

Nari Kim, Pukyong National UniversityFollow
Soo-Jin Lee, Pukyong National UniversityFollow
Eunha Sohn, Korea Meteorological AdministrationFollow
Mija Kim, Korea Meteorological AdministrationFollow
Seonkyeong Seong, Korea Meteorological AdministrationFollow
Seung Hee Kim, Chapman UniversityFollow
Yangwon Lee, Pukyong National UniversityFollow

Document Type

Article

Publication Date

9-18-2024

Abstract

Soil moisture is a critical parameter that significantly impacts the global energy balance, including the hydrologic cycle, land–atmosphere interactions, soil evaporation, and plant growth. Currently, soil moisture is typically measured by installing sensors in the ground or through satellite remote sensing, with data retrieval facilitated by reanalysis models such as the European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis 5 (ERA5) and the Global Land Data Assimilation System (GLDAS). However, the suitability of these methods for capturing local-scale variabilities is insufficiently validated, particularly in regions like South Korea, where land surfaces are highly complex and heterogeneous. In contrast, artificial intelligence (AI) approaches have shown promising potential for soil moisture retrieval at the local scale but have rarely demonstrated substantial products for spatially continuous grids. This paper presents the retrieval of daily soil moisture (SM) over a 500 m grid for croplands in South Korea using random forest (RF) and automated machine learning (AutoML) models, leveraging satellite images and meteorological data. In a blind test conducted for the years 2013–2019, the AutoML-based SM model demonstrated optimal performance, achieving a root mean square error of 2.713% and a correlation coefficient of 0.940. Furthermore, the performance of the AutoML model remained consistent across all the years and months, as well as under extreme weather conditions, indicating its reliability and stability. Comparing the soil moisture data derived from our AutoML model with the reanalysis data from sources such as the European Space Agency Climate Change Initiative (ESA CCI), GLDAS, the Local Data Assimilation and Prediction System (LDAPS), and ERA5 for the South Korea region reveals that our AutoML model provides a much better representation. These experiments confirm the feasibility of AutoML-based SM retrieval, particularly for local agrometeorological applications in regions with heterogeneous land surfaces like South Korea.

Comments

This article was originally published in Water, volume 16, issue 18, in 2024. https://doi.org/10.3390/w16182661

Recommended Citation

Kim, N.; Lee, S.-J.; Sohn, E.; Kim, M.; Seong, S.; Kim, S.H.; Lee, Y. An Automated Machine Learning Approach to the Retrieval of Daily Soil Moisture in South Korea Using Satellite Images, Meteorological Data, and Digital Elevation Model. Water 2024, 16, 2661. https://doi.org/10.3390/w16182661

Copyright

The authors

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 License.